Device and method for performing a diagnostic test

Abstract

A device and method for performing a point of care diagnostic test for detecting and quantifying at least one analyte in a biological sample (e.g., a body fluid). A device may include an immunoassay apparatus and a holder with an adjustable variable angle stage for positioning the immunoassay apparatus relative to a light source and a detector device so as to optimize the angle of incidence and angle of radiation to optimize an elastic light scattering signal from the immunoassay apparatus. The elastic light scattering signal may be used to quantify the amount of the analyte(s) of interest present in the sample. The device is based upon elastic light scattering, so the variation in the angle of incidence and angle of reflection are optimized to maximize signal generation due to elastic light scattering.

What is claimed is: 
     
       1. An analyte detection system, comprising:
 a lateral-flow chromatographic assay cassette that includes a surface configured to detect an analyte in a sample; 
 an illuminating light source positioned and configured to illuminate the surface of the lateral-flow chromatographic assay cassette with at least one wavelength of light in order to yield an elastic light scattering signal in response to the presence of the analyte; 
 a detector device positioned to capture and detect the elastic light scattering signal; 
 a sample holder coupled to the detector device and configured to position the surface of the lateral-flow chromatographic assay cassette in relation to the detector device and the illuminating light source, wherein the sample holder includes a stage configured to position the surface relative to an angle of illumination from the illuminating light source and an angle of detection to the detector device so as to optimize the elastic light scattering signal; and 
 further comprising a computer readable program stored in a computer readable format and electronically coupled to the detector device, wherein the computer readable program is configured to convert the elastic light scattering signal to a numerical value related to the amount of at least one analyte present in the sample. 
 
     
     
       2. The system of  claim 1 , wherein an angle of illumination from the illuminating light source to the surface and an angle of reflection of illuminating light reflecting from the surface to the detector device are each approximately 45°. 
     
     
       3. The system of  claim 1 , wherein at least one wavelength filter is interposed between the illuminating light source and the lateral-flow chromatographic assay cassette. 
     
     
       4. The system of  claim 1 , wherein the illuminating light source comprises at least one of ambient light, sunlight, an LED light, an incandescent lamp, or a gas-discharge lamp. 
     
     
       5. The system of  claim 1 , wherein the illuminating light source is configured to yield at least one wavelength of light selected to convert the signal of the lateral-flow chromatographic assay cassette to a fluorescent emission signal. 
     
     
       6. The system of  claim 1 , wherein the illuminating light source includes at least one focusing apparatus for focusing the light source on the lateral-flow chromatographic assay cassette. 
     
     
       7. The system of  claim 1 , wherein optimizing the elastic light scattering signal includes improving at least one of a signal-to-noise ratio of the elastic light scattering signal or a detection limit for detection of the analyte. 
     
     
       8. The system of  claim 1 , wherein the angle of illumination from the illuminating light source to the surface of the lateral-flow chromatographic assay cassette ranges from about 45° to about 90° and the angle of detection, which is defined by the angle of illumination plus an angle of reflection of illuminating light reflecting from the surface of the lateral-flow chromatographic assay cassette to the detector device, ranges from about 60° to about 110°. 
     
     
       9. The system of  claim 1 , wherein the sample holder is removably coupled to the detector device. 
     
     
       10. A diagnostic testing system, comprising:
 a lateral-flow chromatographic assay cassette that includes a surface having at least one ligand immobilized thereon configured to interact with an analyte of interest to provide a signal related to the presence of the analyte of interest in a sample; 
 a sample holder configured to position the lateral-flow chromatographic assay cassette in relation to a cassette reader that includes:
 an illumination light source, a detector device positioned to capture and detect the signal related to the presence of the analyte, means for transmitting an illuminating light from the illumination source to the lateral-flow chromatographic assay cassette, means for transmitting a signal from the lateral-flow chromatographic assay cassette to the detector device, stage configured to position the surface of the lateral-flow chromatographic assay cassette at an angle relative to an angle of illumination and relative to an angle of detection so as to optimize an elastic light scattering signal captured and detected by the detector device; and 
 further comprising a computer readable program stored in a computer readable format and electronically coupled to the detector device, wherein the computer readable program is configured to convert the elastic light scattering signal to a numerical value related to the amount of at least one analyte present in the sample. 
 
 
     
     
       11. The diagnostic testing system of  claim 10 , wherein the illuminating light source comprises at least one of ambient light, sunlight, an LED light, an incandescent lamp, or a gas-discharge lamp. 
     
     
       12. The diagnostic testing system of  claim 10 , wherein the illuminating light source includes at least one focusing apparatus for focusing the light source on the lateral-flow chromatographic assay cassette. 
     
     
       13. The diagnostic testing system of  claim 10 , wherein the sample holder is configured to allow adjustment of the angle of the lateral-flow chromatographic assay cassette relative to the light source and the detector device. 
     
     
       14. The diagnostic testing system of  claim 10 , wherein a limit of detection for the analyte of interest is within a standard reference range.